1. Field of the Invention
The present invention relates to an image sensor and a digital camera, and more particularly to a charge accumulation-type image sensor, which accumulates charges in accordance with light amounts of incident light, and a digital camera which employs this image sensor.
2. Description of the Related Art
In recent years, with increases in resolutions of solid state imaging devices, such as CCD (charge coupled device) area sensors, CMOS (complementary metal oxide semiconductor) image sensors and the like, demand has rapidly increased for information technology devices with photography functions, such as digital electronic still cameras, digital video cameras, portable telephones, PDAs (personal digital assistants, which are portable information terminals) and the like. Herein, the above-described information devices with photography functions based on solid state imaging devices will be referred to as digital cameras.
Meanwhile, in recent years there have been requests for these various digital cameras to take photographs of non-visible light images as well as conventional photographs of visible light images. For example, if it were possible to take photographs of infrared images, it would be possible to take photographs at night, and suchlike.
Heretofore, as a technology which can be applied in answer to such requests, Japanese Patent Application Laid-Open (JP-A) No. 6-177416 has disclosed a technology of forming an illumination sensor device, which is formed of a diffusion region and an N region on a silicon substrate, forming a separate P region adjacent thereto, and imaging visible light and infrared light at the same surface.
Furthermore, JP-A No. 10-210486 has disclosed a technology which utilizes plural separation components and CCDs, including a separation component such as a cold mirror that separates visible light from non-visible light or the like, to enable imaging of visible light and non-visible light.
However, with the technology disclosed in JP-A No. 6-177416, the two types of sensor device, and electrodes thereof, are disposed at the same light-receiving surface. Therefore, in comparison with a case of receiving only visible light or only non-visible light at the same light-receiving surface, light-receiving areas for both visible light and infrared light are smaller and imaging sensitivity is lowered, which is a problem. Furthermore, with the technology disclosed in the same JP-A No. 6-177416, because refractive indices of optical elements vary in accordance with differences between wavelengths of the light that is incident at the sensors, focusing distances of the visible light and the infrared light differ. Consequently, it is difficult to focus both the visible light and the infrared light with excellent characteristics, which is a problem.
Meanwhile, with the technology disclosed in JP-A No. 10-210486, a plurality of CCDs are required. As well as leading to increases in power consumption and costs, this leads to an increase in size of the equipment, and these are problems.